This invention relates to electronic oscillators and in particular to an electronic oscillator in which current consumption is minimized.
Electronic oscillators, such as a crystal oscillator comprising a piezoelectric crystal and an amplifier element, are well known in the art. Examples of such oscillators are shown in U.S. Pat. Nos. 3,375,466 and 4,039,973. Crystal oscillators tuned to a particular frequency, such as, for example, 32.768 KHz, are typically used in electronic devices such as calculators and watches to provide the requisite clocking signals for the operation of the devices.
One problem associated with small, battery-powered devices, such as electronic wristwatches, is that of reducing the current consumption of the electronic circuitry to enhance the lifetime of the battery power supply. Oscillators used in electronic watches typically draw on the order of 1-2 microamps of current.
Prior art approaches to reducing the current consumption in electronic oscillator systems have generally involved the use of high impedance electrical resistors to prevent direct current from flowing between the positive and negative terminals of the voltage power supply for the oscillator system. Although direct current loss is somewhat minimized, the use of these resistors has the undesirable effect of reducing the oscillator gain, which increases the start-up time of the oscillator system, and increasing the output impedance, which makes the oscillator system more susceptible to random noise gliches.